(_b_) Open cylinder valves. (_c_) Determine which cylinder has the lower pressure by the gages. Open the filling-line valve at the gage showing the lower pressure and fill the pressure tanks to the pressure shown by the gage. Close the valve. Then open the other filling-line valve and fill the pressure tanks until they reach pressures of at least 1,700 pounds per square inch as shown by the gage. (_d_) When the pressure tanks have been filled, close the filling-line valves. Open the bleeders on the charging lines and leave them open until the pressure in the charging lines is released. Then close bleeders. Remove the charging-line fittings from the check valves. Screw the threaded caps on the check valves and tighten caps with a wrench. (_e_) Repeat steps in (_a_) through (_d_) above for as many pairs of empty flame-thrower tanks as require charging. (8) _To insure proper pressure._ Care should be taken to make certain that the compression delivered to the flame-thrower pressure tank is a full 1,700 pounds per square inch. (_a_) If a filling-line valve leaks, tighten the packing nut on the valve with a wrench. (_b_) When the higher pressure shown on the filling-line gages is less than 1,700 pounds per square inch, close the filling-line valve and the cylinder valve on the cylinder having the lower pressure. Remove and replace this cylinder with a fully charged cylinder. With chalk, mark the pressure on the cylinder which has been withdrawn. (9) _After charging._ When charging has been completed: (_a_) Close the filling-line valves. Observe the pressure indicated on each gage and mark the pressure on each cylinder using crayon, chalk, or pencil. (_b_) Close the valves on the cylinders. (_c_) Remove the charging-line fittings from the check valves, replace the threaded caps on the check valves, and tighten caps with a wrench. (_d_) Remove the filling lines from the cylinders. Use two wrenches and take care not to twist or kink the flexible hose. Support the lines during the operation so that their full weight does not hang on the flexible hose during removal. [Illustration: Fig 24. Arrangement of cylinders and lines for charging four flame throwers. Flexible hose (assembly E81-3-6) from service kit is used to connect two filling lines.] (10) _Use of four-place lines._ (Fig 24) The filling and charging lines found in two or more service kits may be combined for more efficient charging of large numbers of pressure tanks. An additional flexible hose is provided in each service kit for connecting two filling lines. The procedure for charging is similar to that described above for the two-place line. Air or nitrogen is taken first from the cylinder with the lowest pressure and last from the cylinder with the highest pressure. See _a_ (2) above. 33. PRECAUTIONS WHEN PRESSURE-CHARGING. Personnel will familiarize themselves with the following precautions: